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  1. #1
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    Exclamation Installing Sleepers and Ply over concrete

    I would like to cover an existing concrete floor (floor has a vapor barrior that was cut thru in places for plumbing work). I was going to use white wood 2 x 2 sleepers attached with tapcon fasters (shimmed as necessary) and 3/4 t & g plywood. what should I do about a vapor barrior and insulation? I dont want to create a moisture problem by adding a second vapor barrior even thou the first is no longer a solid piece. Could I use fiberglass insulation?

  2. #2
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    Default Re: Installing Sleepers and Ply over concrete

    The first question that comes to mind .... what is the purpose of the vapor barrier ( sheet plastic ? ) .... to prevent moisture coming up through the floor?
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
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    Default Re: Installing Sleepers and Ply over concrete

    Personally, unless these openings in the plastic sheet are substantial...I wouldn't worry about them too much. However, it certainly wouldn't do any harm to reseal any loose edges from slits to one another with vapor barrier tape and /or by
    gluing/adhering the edges of the holes down to the concrete with a suitable caulk; one that won't eat up the plastic, but will adhere to it and the crete. (polyurethane caulk or similar) Lay a bead down and press the edges of the sheeting down into it.

    I would personally use treated stock for the sleepers...just in case. Call me Mr. Overkill but if this is a basement and there is ever a plumbing leak under that floor....... ( Sleepers on 16" OC, of course) However, unless you can get KD2 treated stock (kiln dried again after treatment) ..the treated stock will likely arrive fairly wet and so should best be allowed to dry down before installing or by allowing the sleepers to remain exposed for a while after install ( a couple weeks or so if temps are well above freezing) . If you don't do this, you'd be trapping a fair amount of moisture under/inside the floor when you lay down the ply subfloor.

    Tapcons are rated for use with ACQ, so no worries there.

    http://www.concretescrews.com/tapcon-questions.htm

    I would suggest 1 1/2" XPS foamboard for your insulation. It will be a far superior product for your application and will last forever under there. You could consider cutting each strip
    about 1/2" - 5/8" narrow, centering it between the joists and then filling around the perimeter with a canned foam. This would make for a very tight seal. Same for the butt joints at the end of the sheets.

    If the added effort and cost of the canned foam doesn't appeal to you, fit them as tightly as practical and call it a day.

    You do realize that if this floor ever floods...you'll still likely have some problems to contend with? But at least the XPS
    foamboard will survive and so should the treated sleepers.

    Don't know if the 3/4" ply is intended to be the finish floor, so to speak. Even if not, you might still consider screwing it down instead of nailing. This would make it far easier to
    remove if/when the time ever arrives (a flood or similar). Use SS screws for this if using ACQ treated stock for sleepers.

    Leave the so-called coated/ACQ rated screws on the big-box shelf right where they are...is my advice. Have seen them corrode substantially in just 6 months time when in cntact with ACQ.
    Last edited by goldhiller; 08-22-2008 at 11:19 AM.

  4. #4
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    Default Re: Installing Sleepers and Ply over concrete

    Quote Originally Posted by canuk View Post
    The first question that comes to mind .... what is the purpose of the vapor barrier ( sheet plastic ? ) .... to prevent moisture coming up through the floor?
    Yes this was installed when the house was built, this slab is at or above grade

  5. #5
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    Default Re: Installing Sleepers and Ply over concrete

    PS- Be careful when installing those tapcons as you don't want to drill or screw thru any of the plumbing where it might be close enough to the surface to be in danger.

    Also....If this is the subfloor.....do you know what your intended finish floor material will be? Reason I ask is because *if* you intend to put tile down over this floor...the 3/4" ply alone *might* not prove to be sufficient with sleepers on 16" OC...even though it is all supported by concrete. Today's normal construction grade ply is not as well made as it was ten years ago. (poor gluing/production practices which leads to delamination of the layers + unseen internal voids) Too much flex and your grout or tile *could* crack.
    Last edited by goldhiller; 08-22-2008 at 09:20 PM.

  6. #6
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    Default Re: Installing Sleepers and Ply over concrete

    Quote Originally Posted by ****hiller View Post
    PS- Be careful when installing those tapcons as you don't want to drill or screw thru any of the plumbing where it might be close enough to the surface to be in danger.

    Also....If this is the subfloor.....do you know what your intended finish floor material will be? Reason I ask is because *if* you intend to put tile down over this floor...the 3/4" ply alone *might* not prove to be sufficient with sleepers on 16" OC...even though it is all supported by concrete. Today's normal construction grade ply is not as well made as it was ten years ago. (poor gluing/production practices which leads to delamination of the layers + unseen internal voids) Too much flex and your grout or tile *could* crack.
    I am going to cover the entire floor, prior to installing new partition walls. this is a entire rehab project. The concrete floor was not installed very flat or level, this is part of the reason I am thinking about this. The sleepers will give me a chance of leveling the floor.

  7. #7
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    Default Re: Installing Sleepers and Ply over concrete

    Okay, gotcha.

    Another thng which comes to mind and which you might consider in this instance is....

    Rather than laying down the ply over all of your sleepers and then building your partition walls on top of that (basic platform type construction)...you might consider placing the sole plates for the partition walls on top of the sleepers and then fitting your ply up to those sole plates...instead.

    Reason being that *if* anything goes awry under that floor at some point in the future, this approach would make it real easy to remove the subfloor from any given area/room. If the partition walls are built on top of the ply, it wouldn't be as easy to do. You'd end up having to make some cuts to get the ply up and would then end up with those extra seams along the walls when reassembling.

    Just a thought from a BTDT/dealt with that kinda headache guy.

    If doing it the suggested way, it would also allow you to place extra sleepers where necessary under those sole plates(sole plate running parallel to sleepers). This way your partition walls wouldn't tenatively end up sitting on ply right between two sleepers...which could become a problem if you ever did have to cut the subfloor to access underneath it.

    Yes, this means that you'd likely need to add some 2x4 blocking (flat-wise) between the studs to ensure good fastening for your drywall or whatever your chosen wall covering will be. Might all seem unnecessary, but it's just a thought/consideration concerning the future and easy access because frequently enough it seems...something will happen and someone will need to get under there in a hurry.

    Maybe it's all six of one and half-dozen of the other. Your house, your call. <G>
    Last edited by goldhiller; 08-23-2008 at 11:35 AM.

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